The present invention relates to a fuel nozzle system for enabling a gas turbine to start and operate on low-Btu fuels and a method for using a fuel nozzle system to start and operate a gas turbine on low-Btu fuels.
In general, gas turbine engines combust a fuel/air mixture that releases heat energy to form a high temperature gas stream. The turbine converts thermal energy from the high temperature gas stream to mechanical energy that rotates a turbine shaft. The turbine may be used in a variety of applications, such as for providing power to a pump or an electrical generator.
Recently, gas turbines usually are equipped with a fuel nozzle, which supplies fuels for ignition and normal running of the gas turbine. A typical fuel used for igniting and running gas turbines is the natural gas. However, due to the scarcity of natural gas source, it has come to rely more and more on other fuels, such as low-Btu gases. For example, there are industrial gas turbines for steel mills fired on blast furnace gas (BFG) with a small amount of coke oven gas (COG) blending. However, the gas turbine still starts on natural gas or liquid fuel, for example, by using a fuel nozzle having a natural gas tip suitable for igniting natural gas and a BFG tip for firing BFG during normal running of the gas turbine. Starting the BFG gas turbine by igniting natural gas not only consumes premium natural gas but also requires separate ignition fuel system such as oil cartridge and oil tank. Moreover, in some circumstances, there may be no natural gas available at sites, such as in steel mills.
Therefore, it is desired to develop a novel gas turbine fuel nozzle capable of starting on low-Btu fuels such as BFG, COG and syngas, as well as a new method for starting gas turbines on low-Btu fuels by using such a novel gas turbine fuel nozzle.